This claim had already been made explicitly by August Weismann at the end of the nineteenth century, who differentiated between the germplasm of an organism, the tissue that forms the gametes to produce the next generation, and the somatoplasm, the tissues of the rest of the body.

According to this concept, the substance of the body (the somatoplasm) is in each generation produced as an offshoot of the germplasm, or germ-line, so that whatever characteristics are in - herited must be transmitted from the germplasm to the somatic part of the body.